Gate-tuned normal and superconducting transport at the surface of a topological insulator

TL;DR

This paper demonstrates gate-tuned control of normal and superconducting transport of Dirac fermions on a topological insulator surface, revealing Landau level filling and supercurrent modulation in a device setting.

Contribution

It introduces a method to control and observe Dirac fermion transport and supercurrent in topological insulator devices using gating and magnetic fields.

Findings

Landau levels are filled and evolve from electron- to hole-like with gate voltage.

Supercurrent magnitude can be tuned by gating and is minimized at charge neutrality.

Gated devices enable control over Dirac fermion transport at the surface.

Abstract

Three-dimensional topological insulators are characterized by the presence of a bandgap in their bulk and gapless Dirac fermions at their surfaces. New physical phenomena originating from the presence of the Dirac fermions are predicted to occur, and to be experimentally accessible via transport measurements in suitably designed electronic devices. Here we study transport through superconducting junctions fabricated on thin Bi2Se3 single crystals, equipped with a gate electrode. In the presence of perpendicular magnetic field B, sweeping the gate voltage enables us to observe the filling of the Dirac fermion Landau levels, whose character evolves continuously from electron- to hole-like. When B=0, a supercurrent appears, whose magnitude can be gate tuned, and is minimum at the charge neutrality point determined from the Landau level filling. Our results demonstrate how gated nano-electronic devices give control over normal and superconducting transport of Dirac fermions at an individual surface of a three-dimensional topological insulator.